Intermediate filament staining in the cytologic and histologic diagnosis of canine skin and soft tissue tumors.

Formalin-fixed histologic and acetone-fixed cytologic preparations from 87 surgically removed subcutaneous and soft tissue canine tumors were examined for immunoreactivity to cytokeratin, desmin, and vimentin. The avidin-biotin complex (ABC) technique demonstrated immunoreactivity in both preparations, but the intensity and specificity of the reactions were dependent on the primary antibody. Polyclonal antibodies to cytokeratin were more consistent in immunoreactivity than were polyclonal desmin or vimentin antibodies. The monoclonal antibody proved more satisfactory for demonstrating vimentin than the polyclonal antibody. Greater dilutions of primary antibodies may be used on cytologic preparations than on histologic sections. Evaluation of cytologic preparations may be inconclusive due to background staining, scant cellularity, or poor cytoplasmic preservation.